1. Field of Invention
The present invention relates to a traffic information notification system for use by a vehicle and a navigation system.
2. Description of Related Art
One known system relating to technology of navigation systems is the travel plan management system disclosed in Japanese Unexamined Patent Application Publication No. 11-134407. In this travel plan management system, if a travel plan including a starting point, a destination point, and a planned arrival time is input to a navigation apparatus, the travel plan is transmitted to an information center. In accordance with the received travel plan, the information center searches for an optimum route from the starting point to the destination point and calculates the time required for a car to travel along the optimum route. The detected optimum route and the calculated required time are registered in the information center and data indicating the optimum route and the required time is transmitted to the navigation apparatus. In response to receiving the data, the navigation apparatus displays the optimum route and the required time.
If an event occurs at a location along the optimum route, the occurrence of that event can cause traffic congestion. The traffic congestion can cause a problem in the planned travel. If such an event occurs, an optimum route is re-searched and data associated with the re-searched optimum route is transmitted to the navigation apparatus.
In a car navigation system using a travel plan management system according to the above-described technique, if a user of the navigation system specifies a navigation route, the specified route is registered. When traffic congestion occurs on the registered route, the user is informed of the occurrence of traffic congestion.
However, in order to specify a navigation route to be registered, the user has to perform a troublesome manual operation to input data specifying the navigation route to the navigation system.
A notification of an occurrence of traffic congestion is issued each time traffic congestion occurs. If traffic congestion occurs frequently on a registered navigation route, frequent notifications of occurrences of traffic congestion can bother a user.